Research uncovers materials challenges for future chips

SAN FRANCISCO—A team of physicists at McGill University have demonstrated that electrical current may be drastically reduced when wires from two dissimilar metals meet, calling attention to a future technology hurdle for semiconductor design.

The surprisingly sharp reduction in current reveals a significant challenge that could shape material choices and device design in the emerging field of nanoelectronics, according to the researchers, who worked in collaboration with General Motors R&D.

As semiconductor feature sizes continue to shrink, designers of future chips will need to understand how an electrical charge behaves when it is confined to metal wires only a few atom-widths in diameter. As feature sizes dwindle to the level of atoms, the resistance to current no longer increases at a consistent rate as devices shrink, according to the McGill researchers. Instead the resistance "jumps around," displaying the counterintuitive effects of quantum mechanics, according to McGill physics professor Peter Grütter.

"You could use the analogy of a water hose," Grütter said. "If you keep the water pressure constant, less water comes out as you reduce the diameter of the hose. But if you were to shrink the hose to the size of a straw just two or three atoms in diameter, the outflow would no longer decline at a rate proportional to the hose cross-sectional area; it would vary in a quantized [jumpy] way."